Compression and extension of a rolling lobe air spring causes fatiguing damage to the air spring sleeve. The damage accumulates over the life of the air spring until failure of the sleeve occurs. The distribution of stress in the sleeve is an important factor in the durability of the sleeve. When the stress is uniform around the circumference of the sleeve in the rolling lobe, the durability is maximized.
Side load compensating air springs utilize tilting the end cap of the air spring with respect to the axis of the piston/strut. This causes the stress distribution of the sleeve to become elliptical. This is a non-uniform stress distribution in comparison to the uniform stress distribution. More particularly, a stress along the x axis of the spring is different than a stress in the y axis. Further, greater end cap tilt angles for greater side load compensation result in higher non-uniform stress distribution and lower durability.
The durability of the air spring sleeve is reduced by the elliptical or non-uniform stress distribution. The more non-uniform the stress distribution, the more durability is reduced.
Representative of the art is U.S. Pat. No. 5,752,692 (1998) to Crabtree et al. which discloses a chamber portion attached to a tilted closure and a rolling lobe portion of an airsleeve attached to a piston that is transversely mounted.
The prior art air spring causes an elliptical, non-uniform stress distribution in the sleeve which shortens an operating life.
What is needed is a side-load compensating air spring piston having an elliptical cross-section. What is needed is a side-load compensating air spring having a sleeve with a substantially uniform stress distribution in a rolling lobe. The present invention meets this need.